I use main
For VERY competetive terms, both MSN and Google had a site listed at number 1 with NO HEADER TAGS! No H1, H2, H3, etc.
It could be that this site is #1 due to a huge number of inbound links.
My theory is that each page is ranked based on a variety of factors, and each factor earns “points” toward the overall ranking value.
For example, a page might get 2 points for using relevant H1 tags, 2 points for using title tags, 2 points for having a keyword density of exactly 15%, and 2 points for having 5 inbound links. But, if this page had, say, 100 inbound links, maybe it would have received 10 points instead of 2, for that specific factor.
So, based on my example, a page could have no H1 tags (0 points), no title tags (0 points), and a keyword density of 1% (0 points), but if it has 100 inbound links, it still could earn a higher score than the page with the H1, title, etc.
What I would give to have a look at the real, working algorithm….. :highflyer